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Over the history of instrumental strong-motion recording, the largest amplitudes of ground motions recorded to date have had a significant impact on the perception of the largest amplitudes of ground motion considered physically realizable. However, the length of the instrumental recording history is comparatively short, and instrumental recording networks are relatively sparse, which raises the issue of whether the full range of ground motions has been captured in the current global holdings of strong-motion data. Because the answer to this question is quite obviously negative, a more difficult question then arises: How much greater than the largest currently available observation could future ground motions be? The present article explores this issue, drawing on empirical observations, results from numerical simulations, and a statistical exercise involving the sampling of spatially correlated stochastic ground-motion fields. [ABSTRACT FROM AUTHOR]

The article counters the comments of Heriberta Castaños and Cinna Lomnitz on the authors' review of the subject about ground motions. It is believed that Castaños and Lomnitz are focused on criticizing standard probabilistic seismic hazard analysis (PSHA) in general. Analyzed is the comparison of motions recorded at one accelograph station and flipping a coin. Meanwhile, Castaños and Lomnitz are deemed correct that the maximum attainable levels of motion is being limited by finite strength of near-surface materials.